Partially translucent white film having metallized surface

ABSTRACT

An image-bearing element comprising of a white, translucent, metallized film article wherein the film article comprises a flexible, heat resistant, polymeric film material with opposite sides. The film material has deposited on a first side a metal coating which both reflects and transmits visible light and capable of transmitting from about 1% to about 70% of incident visible light cast thereon. The second side of the film material has a white outermost surface and has a visible light opacity of from about 0.5 to about 0.98.

This application is a continuation of Ser. No. 08/184,081 filed on Jan.18, 1994, now abandoned; which is a divisional of Ser. No. 08/087,953filed on Jul. 6 1993, now U.S. Pat. No. 5,300,395; which is a divisionalof Ser. No. 07/497,227 filed on Mar. 22, 1990, now U.S. Pat. No.5,246,812.

BACKGROUND OF THE INVENTION

The present invention relates to partially translucent, white filmshaving a metallized surface. More particularly, the invention relates toflexible sheet articles having a highly reflective surface, and have theability to partially and controlledly transmit diffuse lighttherethrough.

In the art of color proofing, color separations made from an originalimage should represent a faithful reproduction of tonal values, and theproofing methods used to make representations of these halftoneseparations should reproduce the quality seen in the photomechanicallyproduced originals. However, when these high quality color proofingseparations are compared to the output of a high quality printing press,the results do not always correspond. This lack of correspondence is theresult of the printing press producing a halftone dot size on paper thatis different from the halftone dots on the printing plate, or colorseparation itself. The observable result is what is called in the tradeas "dot gain". It is produced by the spreading out of ink on the printedsheet to cover an area different than is represented by the printingplate or color proofing originals. These problems have been recognizedin the printing industry and certain techniques have been developed toadjust for these variations. Color proofing systems are well known andare broadly disclosed in the prior art. The techniques of progressingfrom an original colored artwork through a series of color separations,and the use of these separations to generate color proofing separationsare well known in the art.

In the art of printing, it is desirable to produce a multi-color proofto assist a printer in correcting a set of color separations which willbe used in exposing a series of expensive lithographic printing plates.The proof should reproduce the color quality that will be obtainedduring the printing process. The proof must be a consistent duplicate ofthe desired half tone or line image. Visual examination of a color proofshould reveal the color rendition to be expected from a press using thecolor separations, and any defects on the separations which might needto be altered before making the printing plates.

Color proofs for multicolored printing can be made by using a printingpress which is known as a proof press. This requires that all of theactual printing steps be formed and this conventional method of colorproofing is costly and time consuming. Alternate color proofing methodshave therefore been developed to simulate the quality of press proofs.There are two general types of photoimaging methods, namely the overlaytype and the single sheet type. In the overlay color proofing system, anindependent transparent plastic support is used for producing a coloredimage of each color separation film. A number of such supports carryingthe various colored images of cyan, yellow, magenta and black are thensuperimposed upon each other and placed on a white sheet to produce acolor proof. Examples of this approach are described in U.S. Pat. Nos.3,136,637; 3,211,553; and 3,326,682. In the single sheet color proofingmethod, a color proof is prepared by successively producing images ofthe colors from different color separation films onto a single receiversheet. This is done by using a single opaque support and by applyingtoners, photosensitive solutions, or coatings of photosensitivematerials of corresponding colors to the opaque support in succession.Examples of this approach are described in U.S. Pat. Nos. 3,671,236;4,260,673; 4,366,223; 4,650,738; 4,656,114; and 4,659,642. An advantageof the single sheet type of color proof is that the color is notinfluenced by superimposed plastic supports. This method more closelyresembles actual printing and eliminates the color distortion inherentin the overlay system. Various processes for producing copies of animage embodying photopolymerization and thermal transfer techniques areknown as shown in U.S. Pat. Nos. 3,060,023; 3,060,024; 3,060,025;3,481,736; and 3,607,264. In these processes, a photopolymerizable layercoated on a support is imagewise exposed through a color separation. Thesurface of the exposed layer is then pressed into contact with the imagereceptor sheet and the composite is heated to a temperature above thetransfer temperature of the unexposed portions of the layer. The twoelements are then separated, and the image areas transferred to theimage receptor. U.S. Pat. No. 3,721,557 shows a method of transferringcolored images to a receptor sheet. An image carrying support is pressedagainst a suitable adhesive coated receptor member and subsequently, thecarrier support sheet is stripped to accomplish the transfer of theimage. A fresh layer of adhesive is applied to the receptor for eachsubsequent transfer. U.S. Pat. No. 4,596,757 provides a method fortransferring images or solid colors which are subsequently imaged. Thephotosensitive material comprises a carrier support having sequentiallydisposed thereon a release layer; a colored, photopolymerizable layer;and an adhesive layer. The material can undergo exposure, lamination toa temporary support, wet development, and then lamination to a receptorsheet.

Images can also be produced by a peel apart method. Peel apart colorproofing systems are known to the skilled artisan per se. Peel apartmethods are described in U.S. Pat. No. 4,489,154, where a photosensitivelayer is disposed between two self supporting sheets. Upon exposure,there is an imagewise differential in adhesion of the exposed andunexposed portions of the photosensitive image to one of the two sheetsforming the photosensitive element.

It has been found that to various extents, the substrate on which thefinal image appears, contributes to an increase in apparent dot gain onthe proof. This is disadvantageous since it contributes to theproduction of an image which is not a faithful reproduction of theoriginal image. The prior art has recognized this problem and has soughtto achieve a receiver base for image transfer which does not increaseapparent dot gain. To this end, U.S. Pat. No. 4,579,810 discloses amulticolor proof having a pearlescent support. It has now been foundthat dot gain can be controlled using a partially translucent supportwhich is white on one side and has a spectrally reflective, mirror-likemetallic surface on the opposite side. The white side allows an accuratereflective background base from which to view the colors of the image.White backgrounds, while themselves well known in the art are alsotransmissive to part of the light cast upon them. Since the backgroundmaterials, usually white polyester films, have a certain thickness, theytend to reflect part of this transmitted light back through the image ina diffuse fashion and cause a shadow which is viewed as a gain in dotsize. This invention solves this problem by coating the opposite side ofthe support with a mirror-like metallic coating. This causes theinevitable reflections to be much more coherent rather than diffuse,thereby substantially reducing shadow and hence dot gain. In the firstinstance one would assume that the same result could be attained byemploying a base which is completely opaque. However, it has been foundthat in order to correctly register sequential image separated halftoneimages as is necessary in color proofing, the receiver support must havea certain degree of translucency. The present invention thereforeprovides an improved white receiver base for color proofing images whichpossesses the requisite degree of translucency for image registrationand yet has substantially reduced apparent dot gain.

SUMMARY OF THE INVENTION

The present invention provides a white, partially translucent,metallized film article which comprises a flexible, heat resistant,polymeric film material having first and second opposite sides, saidfilm material having deposited on a first side thereof a metal coatingwhich is spectrally reflective and partially light transmissive in thevisible region of the spectrum, said coating having a thickness of fromabout 10 angstroms to about 200 angstroms, a specular gloss of about 90or more; and being capable of transmitting from about 1% to about 70% ofincident visible light cast thereon; the second side having a whiteoutermost surface, said second side having a visible light opacity offrom about 0.5 to about 0.98. The invention also provides an elementwhich comprises the aforesaid article and an image on the white side ofit.

The invention further provides a white, partially translucent,metallized film article which comprises a flexible, heat resistant,polymeric film material having deposited on one side thereof a metalcoating which is spectrally reflective and partially light transmissivein the visible region of the spectrum, said metal coating having athickness of from about 10 angstroms to about 200 angstroms, a speculargloss of from about 90 or more; and being capable of transmitting fromabout 1% to about 70% of incident visible light cast thereon; and theopposite side of the metal coating having a white surface thereon, saidwhite surface having a visible light opacity of from about 0.5 to about0.98. The white surface can be either a white coated layer on the metalcoating or a white polymeric film sheet. Optionally there can be anadhesive between the metal coating and the white polymeric film sheet.These articles may be used to produce elements which comprise an imagedisposed on white surface.

The invention also provides a method of producing a positive colorproofing image having reduced dot gain which comprises:

(A) providing a photosensitive element which comprises, in order:

(i) a transparent support preferably having an adhesion promotedsurface; and

(ii) a photosensitive composition layer on said adhesion promotedsurface, which photosensitive layer comprises an organic binding resin,a colorant, a photoinitiator, and a free radical polymerizable acrylateor methacrylate component having at least two ethylenically unsaturatedgroups, wherein said binding resin is present in sufficient amount tobind the composition components into a uniform film, and wherein saidcolorant is present in sufficient amount to uniformly color thecomposition, and wherein said photoinitiator is present in sufficientamount to initiate the free radical polymerization of said polymerizablecomponent upon exposure to sufficient actinic radiation, and whereinsaid polymerizable component is present in sufficient amount to provideimage differentiation when the composition is image-wise exposed toactinic radiation; and

(iii) an adhesive layer directly adhered to said colored, photosensitivelayer, which adhesive layer comprises a thermoplastic resin which has aT_(g) in the range of from about 25° C. to about 100° C.; and

providing a receiver base which is a white, partially translucent,metallized film article which comprises a flexible, heat resistant,polymeric film material having first and second opposite sides, saidfilm material having deposited on a first side thereof a metal coatingwhich is spectrally reflective and partially light transmissive in thevisible region of the spectrum, said coating having a thickness of fromabout 10 angstroms to about 200 angstroms, a specular gloss of about 90or more; and being capable of transmitting from about 1% to about 70% ofincident visible light cast thereon; the second side having a whiteoutermost surface, said second side having a visible light opacity offrom about 0.5 to about 0.98; and

(B) either

(i) laminating said adhesive layer to said receiver base at elevatedtemperature and pressure; and then image-wise exposing saidphotosensitive composition through the transparent support to actinicradiation; or

(ii) image-wise exposing said photosensitive composition to actinicradiation; and then laminating said adhesive layer to said receiver baseat elevated temperature and pressure; and

(C) peeling apart said support and said receiver base, therebytransferring the adhesive layer and the image-wise nonexposed portionsof the colored, photosensitive composition to the receiver base whilethe image-wise exposed portions remain on the adhesion promoted surfaceof the support; and

(D) optionally repeating steps (A) through (C) at least once withanother photosensitive element having at least one different coloranttransferred to the adhesive layer and image-wise nonexposed portions ofthe previously processed photosensitive element on said receiver base.

The invention also provides an improved method for forming a coloredimage which comprises:

A. providing a receiver base which is a white, partially translucent,metallized film article which comprises a flexible, heat resistant,polymeric film material having first and second opposite sides, saidfilm material having deposited on a first side thereof a metal coatingwhich is spectrally reflective and partially light transmissive in thevisible region of the spectrum, said coating having a thickness of fromabout 10 angstroms to about 200 angstroms, a specular gloss of fromabout 90 or more; and being capable of transmitting from about 1% toabout 70% of incident visible light cast thereon; the second side havinga white outermost surface, said second side having a visible lightopacity of from about 0.5 to about 0.98; and

B. providing a photosensitive element which comprises in order:

i) a substrate having a release surface; and

ii) a photosensitive layer on said release surface, which photosensitivelayer comprises a light sensitive component selected from the groupconsisting of negative working, polymeric diazonium compounds orpositive working quinone diazide compounds or photopolymerizablecompositions in an amount sufficient to photosensitize the layer; and aresinous binder composition in an amount sufficient to bind the layercomponents into a uniform film; and at least one colorant in an amountsufficient to uniformly color the layer; and

iii) an optional, nonphotosensitive, colorless adhesive layer directlyadhered to said colored photosensitive layer, which adhesive layer has asoftening point in the range of from about 60° C. to about 180° C.; and

C. either

i) laminating said photosensitive element with heat and pressure viasaid photosensitive or adhesive layer of the photosensitive element toone side of said receiver sheet composite; and removing said substrateby the application of peeling forces; and imagewise exposing saidphotosensitive layer to actinic radiation; or

ii) imagewise exposing said photosensitive layer to actinic radiation;and laminating said photosensitive element with heat and pressure viasaid photosensitive or adhesive layer of the photosensitive element toone side of said receiver sheet composite; and removing said substrateby the application of peeling forces; or

iii) laminating said photosensitive element with heat and pressure viasaid photosensitive or adhesive layer of the photosensitive element toone side of said receiver sheet composite; and imagewise exposing saidphotosensitive layer to actinic radiation; and removing said substrateby the application of peeling forces; and thereafter

D. removing the nonimage areas of said photosensitive layer with aliquid developer, which removing is conducted at a temperature at whichsaid photosensitive element is substantially nontacky; and thereafter

E. optionally repeating steps (A) through (D) at least once wherebyanother photosensitive element having at least one different colorant islaminated onto the nonremoved portions of the previously processedphotosensitive layer or layers on the receiver sheet composite.

The invention also provides the photosensitive articles which areproduced by the aforesaid methods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows one embodiment of the inventive film article wherein ametallized coating appears on an integral white polyester sheet.

FIG. 2 shows another embodiment of the invention where the articlecomprises two sheets adhered together. The white sheet is an integralwhite polyester sheet and the other sheet is transparent and has themetallized coating.

FIG. 3 shows yet another embodiment of the invention where the articlehas a transparent polyester sheet with a metallized coating on one sideand a white coating on the other side.

FIG. 4 still another embodiment of the invention where the articlecomprises two sheets adhered together. These are a first transparentpolyester sheet with a metallized coating on one side and a secondtransparent polyester sheet having a white coating on one side.

FIG. 5 shows an image on the white side of the article appearing in FIG.1.

FIG. 6 shows an embodiment of the invention where the article comprisestwo sheets adhered together. The white sheet is an integral whitepolyester sheet and the other sheet is transparent and has themetallized coating. The adhered white polyester sheet is on themetallized coating.

FIG. 7 shows another embodiment of the invention where the article has atransparent polyester sheet with a metallized coating on one side and awhite coating on the metallized coating.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the usual full color proof, four distinct colored images are formed,namely cyan, yellow, magenta, and black. When the images aresuperimposed upon each other, a simulated full color reproductionresults. One begins the process of the present invention by preparing areceiver sheet as mentioned above and then forming an image on it.Preferably the image is formed by laminating, exposing and developing acolored, photosensitive layer on the receiver sheet.

The main support of the film may comprise virtually any materialflexible, self-supporting, heat resistant, polymeric film which canwithstand the laminating and wet or dry development processes usual inthe photographic arts. In the preferred embodiment, the substrate iscomposed of a dimensionally and chemically stable base material whichdoes not significantly change its size, shape, or chemical properties asthe result of the heating, coating, or other treatments which it mustundergo. Polyester sheets are preferred and polyethylene terephthalateis most preferred. In the usual case it has a thickness of from about 1to about 10 mils, a more preferred thickness is from about 2 to about 5mils, and most preferably from about 2 to about 3 mils. As mentionedbefore, in certain embodiments, the polyester sheet is transparent.Suitable films include Hostaphan 3000, available from Hoechst CelaneseCorporation; Hostaphan 4400, 4500, and 4540 available from Hoechst AG.Mylar D, available from DuPont; and Melinex 516, 054, 504,505, 582,available from ICI. They may have subbing layers. Examples of adhesionpretreatment subbing layers are disclosed in U.S. Pat. No. 2,627,088. Inother embodiments, the support is an integral white plastic sheet.Melinex 939 polyester from ICI, is useful for this purpose. This isbasically a customarily produced polyethylene terephthalate film where awhite colorant is incorporated into the polymer melt before extrusionand biaxial orientation.

In the embodiment of FIG. 1, there is shown an integral white whitepolyester sheet 4, which has a metallized coating 2 disposed on onesurface of sheet 4. Metallization processes are well known in the art.Typically, a metal such as aluminum is vapor deposited or otherwiseapplied onto one side of the sheet. One vapor deposition technique isdisclosed in U.S. Pat. No. 4,333,983 which is incorporated herein byreference. Metallized films may be those which are availablecommercially from Madico in Woburn Mass., or Martin Processing inMartinsville, Va.

The metal coating has a thickness of from about 10 angstroms to about200 angstroms, or more preferably from about 20 angstroms to about 80angstroms and most preferably from about 20 angstroms to about 30angstroms. The metal layer on the substrate has a specular gloss of fromabout 90 or more, preferably from about 95 or more and most preferablyfrom about 99 or more as measured by a gloss meter. The metal layer iscapable of transmitting from about 1% to about 70%, more preferablyabout 5% to about 50% and most preferably about 10% to about 20% ofincident visible light cast thereon.

FIG. 2 shows another embodiment of the invention wherein a transparentpolyester sheet 6 having a metallized coating 2 is adhered by a suitableadhesive 8 to a white polyester sheet 4.

The films are adhered by a pressure or heat sensitive adhesive layer.The adhesive is preferably colorless and developer resistant. This layercomprises a major amount of one or more thermoplastic polymers.Virtually any thermoplastic polymer may be used for this purpose.Suitable thermoplastic polymers nonexclusively include vinyl acetalresins such as Butvar B-79 available from Monsanto; acrylic resins suchas Elvacite 2044 available from DuPont; ethylene resins such as Elvax210 available from DuPont; ethylene/vinyl acetate copolymers such asElvax 40-W and 150-W available from DuPont; and vinyl chloride resinssuch as Hostaflex CM 133 available from Hoechst AG. Preferably thepolymer is a vinyl acetate polymer or copolymer. The two films aremerely adhered to each other to form the composite.

In the embodiment disclosed in FIG. 3, a transparent polyester sheet 6is provided with a metallized coating 2, and a white coating 10. Thewhite coating may be any appropriate paint emulsion which is capable ofproducing the aforesaid optical characteristics.

FIG. 4 shows an embodiment having a transparent polyester sheet 6 with ametallized surface adhered by adhesive layer 8 to another transparentpolyester sheet 6 having a white coating 10. Among the embodiments ofFIGS. 1 though 4, clearly the embodiment of FIG. 1 is the most preferredfor its simplicity of construction. Also, since a goal of the inventionis to reduce dot gain caused by dot shadows which is caused by diffusionand reflection through the substrate, the fewer the layers, the lessdiffusion. The second side having the white outermost surface, has avisible light opacity of from about 0.5 to about 0.98, more preferablyfrom about 0.7 to about 0.98 and most preferably about 0.85 to about0.97.

FIG. 5 shows the construction of FIG. 1 which bears an image 12. In theusual case, image 12 actually comprises a series of four or more imageseparated image portions. The image may be produced by any of severalmethods known in the art for image transfer, full layer or peel apartprocessing. The most preferred image preparation methods are thosedescribed in U.S. Pat. No. 4,650,738 and 4,659,642 which areincorporated herein by reference. These methods relate to positive andnegative working photographic elements which broadly comprise aphotographic element which is a colored photosensitive layer on atemporary support and an adhesive layer on the photosensitive layer. Theelement is laminated to the receiver, the temporary support removed andexposed in any order, and then developed. In the usual case anotherphotographic element having another color is then applied to theprevious image.

FIG. 6 shows an embodiment of the invention where the article comprisestwo sheets adhered together. The white sheet 4 is an integral whitepolyester sheet and the other sheet 6 is transparent and has themetallized coating 2. The white polyester sheet 4 is adhered on themetallized coating 2 by an adhesive layer 8.

FIG. 7 shows embodiment of the invention where the article has atransparent polyester sheet 6 with a metallized coating 2 on one sideand a white coating 10 on the metallized coating.

In preparing a photosensitive element, the photosensitive layer broadlycomprises a photosensitizer, a colorant, a binding resin, and otheroptional ingredients such as plasticizers, stabilizers, surfactants,antistatic compositions, uv absorbers, photoactivators, antihalationagents, hydrogen atom donors, exposure indicators, optical brighteners,inert fillers, polymerization inhibitors, spectral sensitizers, andresidual coating solvents.

In one embodiment, photosensitizer is preferably a light sensitive,negative working polymeric diazonium salt. The most preferredphotosensitizer is the polycondensation product of3-methoxy-4-diazo-diphenylamine sulfate and 4,4'-bis-methoxymethyl-diphenyl ether, precipitated as mesitylene sulfonate as taught inU.S. Pat. No. 3,849,392. Other suitable photosensitizers are taught inU.S. Pat. No. 4,436,804. The diazo compounds of choice are preferablysoluble in organic solvents.

In another embodiment, the photosensitizer is preferably a lightsensitive, naphthoquinone diazide. The most preferred photosensitizer isthe ester of bis-(3-benzoyl-4,5,6-trihydroxy phenyl)-methane and2-diazo-1-naphthol-5-sulfonic acid as taught in U.S. Pat. No. 4,407,426.Other suitable photosensitizers are taught in U.S. Pat. No. 4,266,001;3,106,365; 3,148,983 and 3,201,239. The diazo compounds of choice arepreferably soluble in organic solvents.

In yet another embodiment, the photosensitizer comprises aphotopolymerizable monomer or oligomer component, and a photoinitiator.Examples of such photosensitizers are given in U.S. Pat. No. 4,596,757.The photopolymerizable material contained in the colored layer usuallycomprises an addition polymerizable, nongaseous (boiling temperatureabove 100° C. at normal atmospheric pressure), ethylenically-unsaturatedcompounds containing at least two terminal ethylene groups, and beingcapable of forming a high molecular weight polymer by free radicalinitiated, chain propagating addition polymerization. Suitablepolymerizable materials nonexclusively include triethylene glycoldimethacrylate, tripropylene glycol diacrylate, tetraethylene glycoldimethacrylate, diethylene glycol dimethacrylate, 1,4-butanedioldiacrylate, 1,6-hexanediol dimethacrylate, pentaerythritoltetraacrylate, trimethylol propane triacrylate, trimethylol propanetrimethacrylate, di-pentaerythritol monohydroxypentaacrylate,pentaerthritol triacrylate, bisphenol A ethoxylate dimethacrylate,trimethylolpropane ethoxylate triacrylate, and trimethylolpropanepropoxylate triacrylate.

Free radical liberating photoinitiators include any compound whichliberates free radicals on stimulation by actinic radiation. Preferredphotoinitiators nonexclusively include quinoxaline compounds asdescribed in U.S. Pat. No. 3,765,898; the vicinal polyketaldonylcompounds in U.S. Pat. No. 2,367,660; the alpha-carbonyls in U.S. Pat.Nos. 2,367,661 and 2,367,670; the acyloin ethers in U.S. Pat. No.2,448,828; the triarylimidazolyl dimers in U.S. Pat. No. 3,479,185; thealpha-hydrocarbon-substituted aromatic acyloins in U.S. Pat. No.2,722,512; polynuclear quinones in U.S. Pat. Nos. 2,951,758 and3,046,127; and s-triazines in U.S. Pat. No. 4,656,272.

Dyes and/or pigments are included in the photosensitive layer to providecolor to the image areas. Preferred colorants for this invention arepigments rather than dyes. Light fast colorants are preferred. Thepigments are typically dispersed with an organic binder in an organicsolvent or mixture of organic solvents. The pigments may be organic orinorganic. They are ground to a small enough particle size to duplicatethe particle size and color of equivalent inks. The median diameter isgenerally less than 1 micrometer.

Nonexclusive examples of colorants usable in the present invention areas follows: Permanent Yellow G (C.I. 21095), Permanent Yellow GR (C.I.21100), Permanent Yellow DHG (C.I. 21090), Permanent Rubine L6B (C.I.15850:1), Permanent Pink F3B (C.I. 12433), Hostaperm Pink E (C.I.73915), Hostaperm Red Violet ER (C.I. 46500), Permanent Carmine FBB(C.I. 12485), Hostaperm Blue B2G (C.I. 74160), Hostaperm Blue A2R (C.I.74160), and Printex 25. Most of these pigments are products of HoechstAG. They can be used separately or blended for a desired color.

Binders found suitable for the photosensitive layer are styrene/maleicanhydride copolymers and their half esters; acrylic polymers andcopolymers; polyamides; polyvinyl pyrrolidones; cellulose and itsderivatives; phenolic resins; and polyvinyl acetals, such as polyvinylformal, polyvinyl butyral, and polyvinyl propional.

Dyes may be included to spectrally sensitize the photoinitiator, such asdescribed in U.S. Pat. Nos. 4,282,309 and 4,454,218, and European PatentApplications 0,179,448 and 0,211,615.

In the practice of the present invention, the binder component ispreferably present in the photosensitive layer in an amount sufficientto bind the composition components in a uniform mixture and a uniformfilm when it is coated on a substrate. It is preferably present in anamount ranging from about 10% to about 80% based on the weight of thesolids in the layer. A more preferred range is from about 20% to about70%.

In the preferred embodiment, when a diazonium salt or diazide compoundis the photosensitizer component, it is present in the photosensitivelayer in an amount of from about 5 to about 70 percent by weight; morepreferably from about 10 to about 50 percent by weight.

In the practice of the present invention, when a photoinitiator compoundis used, it is preferably present in the photosensitive layer in aamount sufficient to initiate the free radical polymerization of theunsaturated component upon exposure to imaging energy. It is preferablypresent in an amount ranging from about 2% to about 30% based on theweight of the solids in the layer. A more preferred range is from about6% to about 20%.

In the practice of the present invention, the colorant component ispreferably present in an amount sufficient to uniformly color thephotosensitive layer. It is preferably present in an amount ranging fromabout 5% to about 50% based on the weight of the solids in the layer. Amore preferred range is from about 10% to about 40%.

In the practice of the present invention, when an unsaturated componentis used, it is preferably present in the photosensitive layer in anamount sufficient to cause an imagewise latent differential in thepolymerizable composition when it is coated on a substrate and imagewiseexposed to imaging energy. It is preferably present in an amount rangingfrom about 10% to about 60% based on the weight of the solids in thelayer. A more preferred range is from about 15% to about 40%.

Suitable acid stabilizers useful within the context of this inventioninclude phosphoric, citric, benzoic, m-nitro benzoic, p(p-anilinophenylazo) benzene sulfonic acid, 4,4'-dinitro-2,2'-stilbene disulfonic,itaconic, tartaric and p-toluene sulfonic acid and mixtures thereof.Preferably, the acid stabilizer is phosphoric acid.

Exposure indicators (or photoimagers) which may be useful in conjunctionwith the present invention include 4-phenyl-azodiphenylamine, eosin,azobenzene, Calcozine Fuchine, Crystal Violet, and Methylene Blue dyes.Preferably, the exposure indicator is 4-phenylazodiphenylamine.

The photoactivator which may be included in the composition of thisinvention should be an amine-containing photoactivator which combinessynergistically with the free-radical photoinitiator in order to extendthe effective half-life of the photoinitiator, which is normally in theapproximate range of about 10⁻⁹ to 10⁻¹⁵ seconds. Suitablephotoactivators include 2-(N-butoxy) ethyl-4-dimethylamino benzoate,2-(dimethylamino) amino benzoate, and acrylated amines.

A plasticizer may also be included in the composition of this inventionto prevent coating brittleness to keep the composition pliable ifdesired. Suitable plasticizers include dibutylphthalate,dioctylphthalate, triarylphosphate and substituted analogs thereof.

To form a coating composition for the production of the photosensitiveelements, the composition of this invention may be dissolved in asolvent or mixture of solvents to facilitate application of thecomposition to the substrate. Suitable solvents for this purpose mayinclude water, tetrahydrofuran, gamma butyrolactone, glycol ethers suchas propylene glycol monomethyl ether and methyl cellosolve, alcoholssuch as ethanol and n-propanol and ketones such as methyl ethyl ketone.In general, the solvent system is evaporated from the coatingcomposition once it is applied to an appropriate substrate.

However, some insignificant amount of solvent may remain as residue.

In the preferred embodiment, the photosensitive layer has a coatingweight between approximately 0.1 and 5.0 g/m². The most preferred weightis from about 0.5 to 2.0 g/m².

The purpose of the optional adhesive layer on the photosensitive layeris to aid in the transfer of the photosensitive layer and to protect theintegrity of underlying, previous formed images during development ofsubsequent layer or layers. It may be applied to the photosensitivelayer in several different ways. It can be coated directly onto thephotosensitive layer out of organic or aqueous based solvent mixtures,or it can be applied by hot melt extrusion, lamination, or coating. Theoptional adhesive layer preferably comprises a major amount of one ormore thermoplastic polymers and may optionally contain such otherdesired components as uv absorbers, antistatic compositions, opticalbrighteners, inert fillers, and plasticizers. Suitable polymersnonexclusively include vinyl acetal resins such as Butvar B-79 availablefrom Monsanto; acrylic resins such as Elvacite 2044 available fromDuPont; ethylene resins such as Elvax 210 available from DuPont; andvinyl chloride resins such as Hostaflex CM 133 available from HoechstAG. Preferably the polymer is a vinyl acetate polymer or copolymer.Useful polyvinyl acetates nonexclusively include Mowilith DM-6, DM-22,20, 25, 30 and mixtures thereof, available from Hoechst AG. These areusually dispersed in water, or dissolved in methyl isobutyl ketone orn-butyl acetate or other solvent compositions for coating on thephotosensitive layer. It is then dried to a coating weight of from about2 to about 30 g/m², more preferably from about 4 to about 20 g/m². Thelayer may optionally contain a uv absorber such as Uvinul D-50 availablefrom GAF. It may also contain a plasticizer such as Resoflex R-296,available from Cambridge Industries. It may also contain antistats, suchas Gafac and Gafstat available from GAF. It may also contain otherresins such as Nitrocellulose RS 1/2, available from Hercules. Theadhesive layer should not be tacky to the touch, during storage orduring development of the photosensitive element. The layer should betransferable in the range of from about 60° C. to 180° C., preferably60° C. to 120° C., more preferably 60° C. to 100° C. when laminated withheat and pressure. In the preferred embodiment, the thermoplasticpolymer or polymers are present in the adhesive layer in an amount ofgreater than about 50% by weight. The plasticizer may be present in anamount of up to about 30% by weight, the uv absorber up to about 20% byweight, and other resins up to about 50% by weight.

Typical adhesive formulations for the photosensitive elementnonexclusively include.

    ______________________________________                                        I.        Water        50.00                                                            Mowilith DM-22                                                                             50.00                                                  II.       n-butyl acetate                                                                            78.00                                                            Resoflex R-296                                                                             1.00                                                             Mowilith 30  21.00                                                  III.      n-butyl acetate                                                                            68.70                                                            Uvinul D-50  1.30                                                             Mowilith 20  30.00                                                  IV.       n-butyl acetate                                                                            85.00                                                            Mowilith 60  15.00                                                  ______________________________________                                    

In operation, the photosensitive element is laminated to one side of thereceiver sheet composite via the photosensitive layer or adhesive layerof the photosensitive element if present. Lamination may be conducted byputting together the photosensitive element and receiver sheet compositein the proper configuration and then introducing the two materials intothe nip of a pair of heated laminating rollers under suitable pressure.Suitable laminating temperatures usually range from about 60° C. toabout 180° C., preferably about 60° C. to about 120° C. Afterlamination, the substrate is peeled away, usually merely employingmanual peeling forces. The photosensitive layer plus the adhesive layerof the photosensitive element when used thus remains on top of thecomposite.

The photosensitive layer is imagewise exposed by means well known in theart either before or after lamination. Such exposure may be conducted byexposure to a uv light source through a color separation under vacuumframe conditions. Exposures after lamination and support removal arepreferred for emulsion-to-photosensitive layer contact. Mercury vapordischarge lamps are preferred over metal halide lamps. Other radiationsources, such as carbon arc, pulsed xenon, and lasers, may also be used.Light absorbing filters may be used to reduce light scattering in thematerial.

After transfer and exposure, the photosensitive layer is developed bydissolving the nonimage areas in a suitable developer and dried.Suitable developers nonexclusively include:

    ______________________________________                                                         Weight Percent                                               ______________________________________                                        I.     water           95.0                                                          sodium decyl sulphate                                                                         3.0                                                           disodium phosphate                                                                            1.5                                                           sodium metasilicate                                                                           0.5                                                    II.    water           89.264                                                        monosodium phosphate                                                                          0.269                                                         trisodium phosphate                                                                           2.230                                                         sodium tetradecyl sulfate                                                                     8.237                                                  ______________________________________                                    

Any developer solution which satisfactorily removes the nonimage areasof the photosensitive layer after exposure while retaining the imageareas may be used. The selection of developer is well within the abilityof the skilled artisan. Development is performed at temperatures belowthat at which the photosensitive element is nontacky.

The process can then be repeated whereby another photosensitive elementhaving a different color is laminated to the same receiver sheetcomposite over the previously formed image. In the usual case, fourcolored layers are employed to produce a full color reproduction of adesired image. These are cyan, magenta, yellow and black. Optionally onecan laminate a protective layer over the thusly produced image.

In another embodiment of the invention, the image is formed by a drypeel apart development. In the peel apart method, after lamination ofthe photosensitive and adhesive layers and its support to the receiverbase and after exposure of the photosensitive layer, the photosensitivelayer is dry developed by stripping the support from the receiver baseat room temperature with a steady, continuous motion. The preferred peelangle relative to the peel direction is greater than 90°. Thedelamination leaves the photoexposed areas on the temporary support andthe nonexposed areas on the adhesive layer. The adhesive layer remainswith the receiver base. Thus, an image with the adhesive remains on thereceiver base. Another photosensitive layer is laminated via anotheradhesive to the first image on the receiver base. The secondphotosensitive layer has a different color than the first and is exposedthrough the appropriate color separation. After lamination to thereceiver and exposure, the temporary support of the secondphotosensitive layer is removed as was done with the first support. Thesecond image with its adhesive remains with the first image. A third anda fourth image may be added in a manner similar to that used to producethe second image. In the usual case, four colored layers are employed toproduce a full color reproduction of a desired image. These four colorsare cyan, magenta, yellow, and black.

The following nonlimiting examples serve to illustrate the invention.

EXAMPLE 1

A receiver base for a color proof is constructed by coating metallizedpolyester film (20% visible light transmission) with an adhesivesolution of 20% Mowilith 30, 1% Resoflex, and 79% n-butyl acetate byweight. The adhesive is dried and a white polyester film (Melinex994/200 from ICI) is laminated to the adhesive with heat and pressure.Another substrate is made by coating adhesive on Enco PressmatchStandard Receiver Base (available from Hoechst Celanese Corporation,Somerville, N.J.) and laminating Melinex 994/200 to this material asbefore. Pressmatch (Hoechst Celanese) negative proofs are made on thesetwo receiver bases, as well as on Pressmatch (Hoechst Celanese) standardreceiver base using recommended procedures, exposing each color with anUGRA Plate Control Wedge. Dot gain measurements are made for each colorin the final proof with a

Cosar 61 densitometer. The results are summarized in the followingtable:

    ______________________________________                                                           Color                                                      Substrate            M      Y      C    K                                     ______________________________________                                                           Dot Gain at 40% Tint                                       994/200 on metallized polyester                                                                    22%    22%    23%  27%                                   994/200 on Standard Receiver                                                                       25%    22%    24%  28%                                   PRESSMATCH Standard Receiver                                                                       25%    23%    25%  29%                                                      Dot Gain at 80% Tint                                       994/200 on metallized polyester                                                                    11%    11%    11%  13%                                   994/200 on Standard Receiver                                                                       11%    11%    11%  13%                                   PRESSMATCH Standard Receiver                                                                       12%    11%    12%  14%                                   ______________________________________                                    

EXAMPLE 2

A substrate for a color proof is made by coating metallized polyesterfilm (20% visible light transmission) with a 4% weight solution ofpolyvinyl alcohol in water with a #8 wire wound rod. A white pigmentdispersion composed of 40% titanium dioxide pigment, 5% Aquanal P-1resin and 55% solvent (butyrolactone and Dowanol PM) by weight is coatedon top of the polyvinyl alcohol coating with a #10 wire wound rod. Theopacity of the white coating is determined to be 0.88. PressmatchNegative color proofs are made on this substrate and on Pressmatchstandard receiver base, exposing each color with a UGRA Plate ControlWedge in the recommended manner. Dot gain is measured for each color inthe final proof at the 40% and 80% tint patches with a Cosar 61densitometer. The results are summarized in the following table:

    ______________________________________                                                           Color                                                      Substrate            M      Y      C    K                                     ______________________________________                                                           Dot Gain at 40% Tint                                       White dispersion on metallized film                                                                22%    22%    23%  28%                                   PRESSMATCH Standard Receiver                                                                       24%    24%    27%  30%                                                      Dot Gain at 80% Tint                                       White dispersion on metallized film                                                                10%    10%    10%  13%                                   PRESSMATCH Standard Receiver                                                                       11%    12%    12%  14%                                   ______________________________________                                    

EXAMPLE 3

A peel development positive color proofing system is made by coating thefollowing four color solutions on adhesion promoted clear polyester film(Melinex 505 from ICI):

    ______________________________________                                        Composition                                                                   (parts by weight)                                                                             Yellow  Magenta  Cyan  Black                                  ______________________________________                                        Tetrahydrofuran 200     200      200   200                                    Dowanol PM      400     400      400   400                                    Diacetone alcohol                                                                             150     150      150   150                                    Sartomer 399    12      8        8     12                                     RB 779          4       4        4     4                                      Formvar 12/85   4       1        1     --                                     Yellow Formvar dispersion                                                                     150     --       --                                           Magenta Formvar dispersion                                                                    --      200      --    --                                     Cyan Formvar dispersion                                                                       --      --       100                                          Black Formvar dispersion                                                                      --      --       --    200                                    Coating density 0.98    1.33     1.28  1.60                                   (densitometer)                                                                ______________________________________                                    

A separate adhesive film is prepared by coating Mowilith 30 adhesivesolution as in Example 1 directly on slip treated polyester film(Melinex 516 from ICI).

A substrate is prepared by coating metallized polyester film (20%visible light transmission) with a Mowilith 30 adhesive solution on themetal side as in Example 1 above. A sheet of Melinex 994/200 whitepolyester film is laminated to the dried adhesive at 170° F. Four colorproofs are prepared on this substrate and on Pressmatch standardreceiver base by laminating a layer of the Mowilith 30 adhesive to theproofing substrate and then peeling off the Melinex 516 carrier sheet. Apiece of the magenta color film is laminated to the adhesive layer andthen exposed through a UGRA Plate Control Wedge through the Melinex 505polyester film. After exposure, the clear Melinex 505 is peeled away,leaving a positive image. The following layers are applied, imaged anddeveloped similarly. A Pressmatch Gloss cover sheet is applied to thefinal proof. The dot gain is measured at the 40% and 80% tint patcheswith a X-Rite 418 densitometer. The results are summarized in thefollowing table:

    ______________________________________                                                           Color                                                      Substrate            M      Y      C    K                                     ______________________________________                                                           Dot Gain at 40% Tint                                       Melinex 994/200 on metallized film                                                                 15%    14%    19%  23%                                   PRESSMATCH STANDARD  18%    20%    25%  28%                                   Receiver                                                                                         Dot Gain at 80% Tint                                       Melinex 994/200 on metallized film                                                                 10%    --     11%  12%                                   PRESSMATCH Standard Receiver                                                                       11%    11%    13%  14%                                   ______________________________________                                    

EXAMPLE 4

Four color proofs are made as in Example 3, except the proofs are madeon Melinex 052 clear polyester as the substrate. A Pressmatch TransferGloss cover sheet is applied to the finished proof and the proofs arepeeled off of the Melinex 052 receiver base. The proofs are thenlaminated to the same 2 substrates as in Example 3 and the temporarysupport is peeled from the cover sheet. The dot gain is again measuredon the two supports as in Example 3. The results are as follows:

    ______________________________________                                                           Color                                                      Substrate            M      Y      C    K                                     ______________________________________                                                           Dot Gain at 40% Tint                                       Melinex 994/200 on metallized film                                                                 18%    21%    20%  22%                                   PRESSMATCH STANDARD  21%    22%    25%  25%                                   Receiver                                                                                         Dot Gain at 80% Tint                                       Melinex 994/200 on metallized film                                                                 11%    11%    12%  13%                                   PRESSMATCH Standard Receiver                                                                       12%    11%    14%  14%                                   ______________________________________                                    

What is claimed is:
 1. An image-bearing element which comprises a whitetranslucent, metallized film article, wherein the article comprises aflexible, heat resistant, polymeric film material having first andsecond opposite sides, said film material having deposited on a firstside thereof a metal coating which is both light reflective and lighttransmissive in the visible region of the spectrum, wherein said coatinghas a thickness of from about 10 angstroms to about 200 angstroms, aspecular gloss of from about 90 or more, and is capable of transmittingfrom about 1% to about 70% of incident visible light cast thereon; andwherein of said film material the second side has a white outermostsurface, said second side having a visible light opacity of from about0.5 to about 0.98, and having an image on the outermost surface of thesecond side.
 2. The element of claim 1 wherein said polymeric filmmaterial comprises a single transparent polymeric film sheet and a whitecoating forming said white outermost surface of said second side.
 3. Theelement of claim 2 wherein the image is a halftone image comprisinghalftone dots.
 4. The element of claim 1 wherein said polymeric filmmaterial comprises a white polymeric film sheet which is whitethroughout its entirety.
 5. The element of claim 4, wherein the image isa halftone image comprising halftone dots.
 6. The element of claim 1wherein said polymeric film material comprises first and secondpolymeric film sheets adhered at an interface and said first and secondsides of said polymeric film material are respectively the sides of saidfirst and second polymeric film sheets opposite to said interface. 7.The element of claim 6 wherein said second polymeric film sheet istransparent, and comprises a white coating forming said white outermostsurface of said second side.
 8. The element of claim 7 wherein the imageis a halftone image comprising halftone dots.
 9. The element of claim 6wherein said second polymeric film sheet is white throughout itsentirety.
 10. The element of claim 9 wherein the image is a halftoneimage comprising halftone dots.
 11. The element of claim 6 wherein theimage is a halftone image comprising halftone dots.
 12. The element ofclaim 1 wherein the image is a halftone image comprising halftone dots.13. An image-bearing element which comprises a white translucent,metallized article, wherein the article comprises a flexible, heatresistant, polymeric film material having deposited on one side thereofa metal coating which is both light reflective and light transmissive inthe visible region of the spectrum, wherein said metal coating has athickness of from about 10 angstroms to about 200 angstroms, a speculargloss of from about 90 or more, and is capable of transmitting fromabout 1% to about 70% of incident visible light cast thereon; andwherein the side of the metal coating opposite from the polymeric filmmaterial has a white surface thereon, said white surface having avisible light opacity of from about 0.5 to about 0.98, and having animage on the white surface on the metal coating.
 14. The element ofclaim 13, wherein the white surface comprises a white coated layer onthe metal coating.
 15. The element of claim 14 wherein the image is ahalftone image comprising halftone dots.
 16. The element claim 13wherein the white surface comprises a white polymeric film sheet. 17.The element of claim 16 further comprising an adhesive between the metalcoating and the white polymeric film sheet.
 18. The element of claim 17wherein the image is a halftone image comprising halftone dots.
 19. Theelement of claim 16 wherein the image is a halftone image comprisinghalftone dots.
 20. The element of claim 14 wherein the image is ahalftone image comprising halftone dots.